debt is one of the most important and misunderstood tools a young profitable bootstrapped company has at its command. a proper understanding of the different forms of debt, how to raise it, how to service it, what to use it for, and what kind of revenues/growth to support with it is absolutely critical for a company to succeed.
the bottom line is spending huge amounts of your own cash is incredibly reckless and dangerous, and is not the kind of thing a small, successful, profitable, growing company that has employees, suppliers, and customers (all to ANSWER TO) should be doing. to a certain extend, building a company is about injecting yourself as seamlessly as possible into the existing network of cash flows and money and increasing that magnitude over time. it's incredibly hard to achieve this kind of bootstrap (verging on the impossible) without either equity or debt.
real businesses in the real world require capital goods and services, on time, on budget, and guaranteed. debt is a mechanism for getting those goods and services in a reliable manner that has successfully been used for thousands upon thousands (nobody knows for sure - read david graeber) of years. the miraculous thing is it turns the time value of money into something you can leverage now. also - interest rates for commercial debt are not the same as interest rates for personal or consumer debt - it differs in one very important function - commercial debt is supposed to increase profits so it very much depends on what the opportunity you are trying to finance is. consumer debt is a dead end and you better go in with eyes wide open - you're simply spending money on nice things. the same is not true with commercial debt which has an infinite number of permutations regarding motivation and returns.
every successful company carries some kind of debt. every single one. doesn't matter if it's the spread on your payroll, net 30 invoices from your suppliers, amex charge card debt, garden variety credit card debt, structured loans, capital leases, or a simple "iou" to the local coffee shop for your daily commissary deliveries, it's a fundamental property of how people interact with each other in the real world.